Downhole shape memory alloy actuator and method

ABSTRACT

A downhole actuator includes, a sleeve, a mandrel, and at least one of the sleeve and the mandrel is in operable communication with a downhole tool to be actuated. The actuator further includes, a follower disposed at one of the sleeve and the mandrel, a pathway disposed at the other of the sleeve and the mandrel, the pathway being receptive to the follower and configured to cause rotational motion and limit a stroke length between the sleeve and the mandrel in response to longitudinal motion between the follower and the pathway. The actuator also has a shape memory alloy in operable communication with the sleeve and the mandrel configured to longitudinally move the sleeve in relation to the mandrel in response to temperature changes thereof.

BACKGROUND

Downhole actuators employ a variety of mechanisms to generate relativemotion to cause actuation. One such mechanism is a Shape Memory Alloy(SMA). A shape memory alloy changes shape in response to changes intemperature. Actuators employing shape memory alloys allow operators toactuate downhole tools in response to changing a temperature of a shapememory alloy employed therein. Typical shape memory alloy actuators arelimited to a single actuation stroke length. Methods and systems topermit multiple actuation stroke lengths with a single shape memoryactuator would be well received in the industry.

BRIEF DESCRIPTION

Disclosed herein is a downhole actuator. The actuator includes, asleeve, a mandrel, and at least one of the sleeve and the mandrel are inoperable communication with a downhole tool to be actuated. The actuatorfurther includes, a follower disposed at one of the sleeve and themandrel, a pathway disposed at the other of the sleeve and the mandrel,the pathway being receptive to the follower and configured to causerotational motion and limit a stroke length between the sleeve and themandrel in response to longitudinal motion between the follower and thepathway. The actuator also has a shape memory alloy in operablecommunication with the sleeve and the mandrel configured tolongitudinally move the sleeve in relation to the mandrel in response totemperature changes thereof.

Further disclosed herein is a method of actuating a downhole tool. Themethod includes, altering a dimension of a shape memory alloy withaltering temperature thereof, displacing a sleeve in relation to amandrel, the sleeve and the mandrel are in operable communication withthe downhole tool. The downhole tool further includes, repositioning afollower disposed at one of the sleeve and the mandrel within a pathwaydisposed at the other of the sleeve and the mandrel, and limiting astroke of the sleeve in relation to the mandrel with the follower in thepathway.

BRIEF DESCRIPTION OF THE DRAWINGS

The following descriptions should not be considered limiting in any way.With reference to the accompanying drawings, like elements are numberedalike:

FIG. 1 depicts a cross-sectioned perspective view of a downhole shapememory alloy actuator disclosed herein;

FIG. 2 depicts a perspective view of a mandrel of the downhole actuatorof FIG. 1 having a multi-track pathway;

FIG. 3 depicts a cross-sectional side view of the downhole actuator ofFIG. 1 in operable communication with a downhole tool; and

FIG. 4 depicts a cross-sectional perspective view of an alternatedownhole shape memory alloy actuator disclosed herein.

DETAILED DESCRIPTION

A detailed description of one or more embodiments of the disclosedapparatus and method are presented herein by way of exemplification andnot limitation with reference to the Figures.

Referring to FIG. 1, an embodiment of a downhole actuator 10 disclosedherein is illustrated. The downhole actuator 10 includes, a sleeve 14having a follower 18, shown herein as a pin, engagable with a pathway22, shown herein as a slot, of a mandrel 26. In this embodiment, themandrel 26 is made of a shape memory alloy (SMA) that changes shape withchanges in temperature. A collar 30 fixes a distal end portion 34 of thesleeve to a distal end portion 38 of the mandrel 26. As such, changes inlength of the mandrel 26, due to changes in temperature thereof, causerelative motion between the pin 18 and the slot 22. The engagement ofthe pin 18 within the slot 22 limits longitudinal stroke length whilecontrolling rotational movement therebetween. This engagement alsocauses the actuator 10 to have multiple stroke lengths as will bedescribed in detail below. These multiple stroke lengths can actuate adownhole tool (not shown) that is operably connected to at least one ofthe sleeve 14 and the mandrel 26.

The shape memory alloy mandrel 26, in this embodiment, is configured toreduce a longitudinal length thereof in response to an increase intemperature. As such, heating of the mandrel 26 causes the slot 22 tomove to towards the collar 30 while the pin 18 remains substantiallystationary with respect to the collar 30. Conversely, cooling of themandrel 26 will allow the mandrel 26 to be reshaped by external forcesapplied thereto. A biasing member 42, illustrated in this embodiment asa series of spring washers, will move the slot 22 away from the collar30 while the pin 18 again remains substantially stationary, therebyelongating the mandrel 26 in the process. Alternate embodiments,however, can use shape memory alloys that function in reverse to that ofthe mandrel 26 such that instead of a reduction in a longitudinal lengththereof there is an increase in a longitudinal length thereof inresponse to an increase in temperature of the shape memory alloy.Additionally, alternate embodiments may employ shape memory alloys thathave a two-way memory effect. Use of such a shape memory allow canpermit the slot 22 of the downhole actuator 10 to move in bothdirections without the use of a biasing member 42 since the shape memoryalloy itself would provide driving forces needed to drive the actuator10 in both directions.

Referring to FIG. 2, the slot 22 of the mandrel 26, receptive to the pin18, is illustrated in greater detail. The slot 22 has multiple tracks46A-46E to control rotational and longitudinal motion of the mandrel 26in relation to the sleeve 14. For example, the pin 18 may initially bein contact with end 44A of track 46A. Heating of the mandrel 26, in thisembodiment, causes it to longitudinally contract thereby moving the pin18 along track 46A until the pin 18 contacts the track 46B, which isangled and thereby causes the mandrel 26 to rotate (counterclockwise asviewed from the right side of the mandrel 26 in this figure). Therotation continues until the pin 18 enters the track 46C, which isstraight, so the rotation stops even as the longitudinal contraction ofthe mandrel 26 continues until the pin 18 contacts the end 44B. This isa stable configuration as long as a force urging the pin 18 towards end44B is maintained. Removing the heating applied to the shape memoryalloy mandrel 26, in this embodiment, allows the urging force of thebiasing member 42 (FIG. 1) to move the pin 18 in the opposite directionalong the track 46C until the pin 18 contacts the angled track 46D atwhich point the mandrel 26 will again rotate (in the counterclockwisedirection) until the pin 18 enters the straight track 46D at which pointthe rotation ceases and only longitudinal motion continues. Thelongitudinal motion ceases when the pin 18 contacts the end 44C of thetrack 46D. The pin 18 butted against the end 44C is also a stableconfiguration as long as a biasing force is urging the pin 18 towardsthe end 44C. The slot 22, having multiple tracks 46A-46E is oftenreferred to as a J-slot.

As mentioned above the actuator 10 has multiple stroke lengths. Themultiple stroke lengths are due to the ends 44A-44C being positioned atdifferent locations along the mandrel 26. For example, the end 44A ispositioned along the mandrel 26 at a different location than end 44C.This is made clearer by observing a difference in a dimension 48A, fromthe end 44A to a shoulder 52, than a dimension 48C, from the end 44C tothe shoulder 52. By simply setting these ends 44A-44C and any additionalends in a similar manner, an operator can set multiple actuation stokelengths in the downhole actuator 10. An actuator 10 having multipleactuation stroke lengths and positions can be useful for actuatingdifferent downhole tools as will be discussed with reference to FIG. 3below.

Although the embodiment illustrated herein has the pin 18 fixed to thesleeve 14 and the slot 22 located on the mandrel 26, alternateembodiments could reverse this relationship and have the pin 18 fixed tothe mandrel 26 and the slot 22 located on the sleeve 14. Additionally,since actuation of the actuator 10 is defined by relative motion betweenthe sleeve 14 and the mandrel 26, an alternate embodiment of theactuator 10 could reverse which of these two parts, the sleeve 14 andthe mandrel 26, is made from the shape memory alloy. For example,embodiments could have the sleeve 14 made from a shape memory alloywhile the mandrel 26 is not. Embodiments of downhole actuators employingthe foregoing reversals would allow actuation in a similar fashion tothe embodiment illustrated herein, albeit in an opposite direction.Additionally, the relative rotational motion between the sleeve 14 andthe mandrel 26 could be employed as the motion of actuation as opposedto the longitudinal motion.

Referring to FIG. 3, the downhole actuator 10 is shown attached to adownhole tool 56, illustrated here as a flow control valve. The valve 56includes a piston 60, threadably attached to the mandrel 26, that islongitudinally movable and sealingly engaged within a tubular 64. Thetubular 64 has a plurality of ports 68 through a wall 72 thereof.Varying the longitudinal position of the piston 60 with respect to theports 68 varies the amount of area of the ports 68 occluded by thepiston 60. As such, the open area of the ports 68 that allows flowtherethrough between an inner portion 74 and an outer portion 78 of thetubular 64 is varied as well to create a throttling effect of the flowcontrol valve 56.

The valve 56 as illustrated is in a closed configuration with themandrel 26 positioned to the right in the view of FIG. 3 due to thebiasing member 42 biasing the mandrel 26 to the right. In this closedconfiguration the pin 18 is positioned in a track 46 of the slot 22 thatpermits positioning the piston 60 to this position. Opening of the valve56 is initiated by increasing temperature of the shape memory alloymandrel 26 with a heater 82, depicted here as an electrical heatingelement. The increase in temperature of the mandrel 26 causes; alongitudinal shortening of the mandrel 26, an increased compression ofthe biasing member 42, movement of the piston 60 toward the left, andrelative motion of the pin 18 within one of the tracks 46A-46E of theslot 22. With sufficient heating and stroke length produced by the shapememory alloy such motion will continue until the pin 18 contacts an end44 of a track 46. Accordingly, an operator can set the parameters of theforegoing structure to open the ports 68 of the valve 56 a desirableamount. Additional open settings of the valve 56 can be achieved throughcooling of the shape memory alloy mandrel 26 (possibly by simplyremoving energy supplied to the heater 82) and allowing the biasingmember 42 to stroke the pin 18 in the opposite direction relative to theslot 22 until another of the ends 44 is contacted. In so doing thenumber of partially opened settings of the valve 56 is limited only bythe physical limitations of adding more of the tracks 46 to the mandrel26.

Referring to FIG. 4, an alternate embodiment of a downhole actuator 110disclosed herein is illustrated. The downhole actuator 110 is similar tothe downhole actuator 10 and as such like elements are designated withthe same reference characters. The downhole actuator 110 includes, thesleeve 14 having the follower 18, shown herein as a pin, engagable withthe pathway 22, shown herein as a slot of the mandrel 126, and a shapememory alloy member 128. In this embodiment, unlike in the actuator 10,the mandrel 126 is a separate component from the shape memory alloymember 128 that changes shape with changes in temperature. In theactuator 10 the shape memory alloy mandrel 26 reduced in length with anincrease in temperature thereof. In contrast, in the actuator 110 theshape memory alloy member 128 increases in length with an increase intemperature thereof. Since the shape memory alloy member 128 contacts acap 132 of the sleeve 14, the increase in length of the shape memoryalloy member 128 causes the mandrel 126 to move in a direction away fromthe cap 132, thereby moving the slot 22 in relation to the pin 18, in asimilar fashion as to that of actuator 10. This movement also causes aportion 136 of the mandrel 126, on a side opposite of the shape memoryalloy member 128, to move in a direction away from the cap 132,compressing the biasing member 42 against stop 140 in the process. Thebiasing member 42 provides a force against the shape memory alloy member128 to return it to its shorter configuration upon reduced temperaturethereof. The slot 22 is thereby moveable in a back and forth fashion, inrelation to the pin 18, in response to heating and cooling of the shapememory alloy member 128. The slot 22, and the pin 18 engaged therewith,is configured to rotate the sleeve 18 in relation to the mandrel 126resulting in a plurality of settable stroke lengths of movementstherebetween.

While the invention has been described with reference to an exemplaryembodiment or embodiments, it will be understood by those skilled in theart that various changes may be made and equivalents may be substitutedfor elements thereof without departing from the scope of the invention.In addition, many modifications may be made to adapt a particularsituation or material to the teachings of the invention withoutdeparting from the essential scope thereof. Therefore, it is intendedthat the invention not be limited to the particular embodiment disclosedas the best mode contemplated for carrying out this invention, but thatthe invention will include all embodiments falling within the scope ofthe claims. Also, in the drawings and the description, there have beendisclosed exemplary embodiments of the invention and, although specificterms may have been employed, they are unless otherwise stated used in ageneric and descriptive sense only and not for purposes of limitation,the scope of the invention therefore not being so limited. Moreover, theuse of the terms first, second, etc. do not denote any order orimportance, but rather the terms first, second, etc. are used todistinguish one element from another. Furthermore, the use of the termsa, an, etc. do not denote a limitation of quantity, but rather denotethe presence of at least one of the referenced item.

1. A downhole actuator comprising: a sleeve; a mandrel, at least one ofthe sleeve and the mandrel being in operable communication with adownhole tool to be actuated; a follower disposed at one of the sleeveand the mandrel; a pathway disposed at the other of the sleeve and themandrel, the pathway being receptive to the follower and configured tocause rotational motion and limit a stroke length between the sleeve andthe mandrel in response to longitudinal motion between the follower andthe pathway; and a shape memory alloy in operable communication with thesleeve and the mandrel configured to longitudinally move the sleeve inrelation to the mandrel in response to temperature changes thereof. 2.The downhole actuator of claim 1, wherein the pathway has a plurality oftracks receptive of the follower and each of the plurality of tracksdefines a unique stroke limit.
 3. The downhole actuator of claim 2,wherein each of the plurality of tracks causes rotational indexing ofthe sleeve in relation to the mandrel with each longitudinal stroke. 4.The downhole actuator of claim 1, further comprising a biasing member inoperable communication with the sleeve and the mandrel to cause relativemovement between the sleeve and the mandrel in a direction counter tothat of the shape memory alloy.
 5. The downhole actuator of claim 1,wherein the follower is a pin and the pathway is a slot.
 6. The downholeactuator of claim 1, wherein increases in temperature of the shapememory alloy cause a decrease or increase in a longitudinal dimensionthereof.
 7. The downhole actuator of claim 1, wherein the shape memoryalloy is configured to reverse the longitudinal motion between thesleeve and the mandrel in response to additional temperature changes ofthe shape memory alloy.
 8. The downhole actuator of claim 1, wherein thesleeve and the mandrel are connectable to the downhole tool such thatrotational motion between the sleeve and the mandrel cause actuation ofthe downhole tool.
 9. The downhole actuator of claim 1, wherein thepathway is a J-slot.
 10. The downhole actuator of claim 1, wherein theshape memory alloy is at least one of the sleeve and the mandrel. 11.The downhole actuator of claim 1, wherein the longitudinal motionbetween the sleeve and the mandrel is greater at a first portion of thesleeve and a first portion of the mandrel than at a second portion ofthe sleeve and a second portion of the mandrel.
 12. The downholeactuator of claim 1, further comprising a heater in operablecommunication with the shape memory alloy.
 13. A method of actuating adownhole tool, comprising: altering a dimension of a shape memory alloywith altering temperature thereof; displacing a sleeve in relation to amandrel, the sleeve and the mandrel being in operable communication withthe downhole tool; repositioning a follower disposed at one of thesleeve and the mandrel within a pathway disposed at the other of thesleeve and the mandrel; and limiting a stroke of the sleeve in relationto the mandrel with the follower in the pathway.
 14. The method ofactuating a downhole tool of claim 13, wherein the repositioning thefollower within the pathway includes rotationally indexing the sleeve inrelation to the mandrel.
 15. The method of actuating a downhole tool ofclaim 14, wherein the rotationally indexing repositions the followerinto a different track of the pathway.
 16. The method of actuating adownhole tool of claim 15, wherein each different track has a differentstroke limit.
 17. The method of actuating a downhole tool of claim 13,wherein the altering temperature is an increasing of temperature. 18.The method of actuating a downhole tool of claim 13, wherein thealtering of the dimension is a shortening or lengthening of alongitudinal dimension.
 19. The method of actuating a downhole tool ofclaim 13, further comprising: further altering temperature of the shapememory alloy; and reshaping the shape memory alloy; and repositioningthe follower within the pathway.
 20. The method of actuating a downholetool of claim 13, wherein a reshaping of the shape memory alloy is inresponse to biasing the shape memory alloy.